Clear Lacquers

Table IX shows that in clear lacquers for metals, "Elvacite" 2028 offers performance far superior to general purpose acrylic resins. The overall performance, especially for bright metals such as silver, copper and brass, is superior to a competitive high adhesion acrylic resin. This rating is based on appearances under use conditions which include exposure to liquid water or aqueous solutions, high concentrations of moisture vapor and protection of the substrate from discoloration by atmospheres containing sulfur compounds. The lacquers used for these tests were prepared according to Formula 1 (page 21 ). Note that the lacquer prepared from "Elvacite" 2028 was applied at much higher solids than the competitive high adhesion acrylic, yet developed hardness more rapidly. Modification of the solvent system resulted in film which developed 24-hour Sward Rocker hardness of 32 with 2028 compared to 12 with the competitive resin.

As demonstrated in Table X, clear coatings of "Elvacite" 2014 show good adhesion, flexibility, and corrosion resistance even on untreated, unprimed aluminum. The chromate conversion coatings widely used as prepaint treatments for aluminum, e.g., "Alodine" 1200S^**and "Bonderite" 721,^***further enhance the adhesion and effective flexibility of coatings of "Elvacite" 2014 and extend the range of conditions under which the coatings show excellent performance.

For spray application, "Elvacite" 2014 can be diluted to 15% solids with the general-purpose thinner on page 12. The "4-2-1" thinner shown on page 12 is suggested for use with "Elvacite" 2014 in formulating to comply with air pollution regulations. Dilution to 15.5% solids by weight with "4-2-1" thinner reduces the toluene content of the final solvent system to 20% by volume. The diluted solution may require further modification for satisfactory spray application.

"Elvacite" 2014 and 2028 are also useful in coatings for bright metals such as brass, copper, and silver. For example, Formula 1 (page 21), has shown excellent outdoor durability on brass and copper. This lacquer can be thinned for spray application as noted, or adapted for aerosol application by modifying the volatile portion.

Where some sacrifice in light resistance and gloss retention can be tolerated, "Elvacite" 2014 and 2028 may be combined with nitrocellulose to reduce cost and promote fast solvent release for quick drying. Blends containing 15-20% nitrocellulose based on total solids are suggested for trial. Coatings based on "Elvacite" 2014 or 2028 and nitrocellulose in this proportion have shown good resistance to yellowing on exposure to ultraviolet light. High gloss lacquers utilizing "Elvacite" 2552 may be formulated based on Formula 8 (page 23).

"Elvacite" 2013 may be used alone or combined with "Elvacite" 2014 for greater economy or to obtain a harder finish. The harder copolymers show good tolerance for diluents. As a result of their lower inherent viscosity, they permit higher solids content for a given viscosity and release solvent more rapidly than "Elvacite" 2014. On metals with a high thermal coefficient of expansion, however, coatings of "Elvacite" 2014 are more resistant than "Elvacite" 2013 to cracking on prolonged exposure under conditions involving severe temperature fluctuations. Relatively thin coatings, i.e., 0.3 mil or less, generally show better stress-crack resistance than thicker films.

In cases where the maximum tolerance for low cost or nonpolluting diluents are required, "Elvacite" 2028 is the best of the copolymer resins for coatings on ferrous and nonferrous metals, wood and other substrates. High levels of ethanol, isopropanol and mineral spirits of low aromatic content are useful with this resin.

Elvacite" 2044 acrylic resin shows outstanding adhesion to aluminum. Clear lacquers with good outdoor durability can be prepared by blending this tough, flexible, butyl methacrylate resin with half-second nitrocellulose to increase hardness and speed solvent release. Formula 3 (page 22), for example, can be applied to aluminum to give coatings that pass "Scotch" tape adhesion, mortar resistance, and 100% humidity tests. Although "Elvacite" 2044 is a relatively high molecular weight resin, it can be sprayed when properly formulated. Film properties can be varied by adjusting the ratio of nitrocellulose to "Elvacite" 2044 in Formula 3 (page 22). Lowering the nitrocellulose content improves resistance to yellowing on exposure to ultraviolet light, but reduces film hardness as shown in Table XI. Resistance to yellowing can be improved by adding a light screen such as "Uvinul" N-35 or reducing the nitrocellulose content to 25 percent of the binder.